Method and apparatus for determining the contact position in a refiner

ABSTRACT

Methods for determining the contact position between a pair of relatively rotating refining surfaces are disclosed including detecting the heat radiating from the initial contact between the pair of refining surfaces during relative rotation therebetween in order to generate an output signal and utilizing the output signal to determine the contact position. Apparatus for determining the contact position is also disclosed.

FIELD OF THE INVENTION

The present invention relates to a method and an apparatus fordetermining the contact position for the refining surfaces on twoopposed refining discs rotating relative to one another in a discrefiner. Determination or indication of this position thus takes placewhen the gap between the refining surfaces is zero.

BACKGROUND OF THE INVENTION

A disc refiner generally comprises two opposed refining discs, which areprovided with exchangeable refining elements which constitute therefining surfaces of the refiner. In disc refiners in which wood chipsare to be refined into paper-making pulp, the refining is carried outbetween the two refining discs, which are thus kept at a definitedistance from each other. Depending on the type of refiner beingutilized, one or both of the refining discs are mounted on a rotaryaxle. These axles are driven by motors which are intended to rapidlyrotate the refining discs, and the distance between the refining discs(gap) is adjusted by means of hydraulics, and is measured by means ofspecialized measuring systems. Due to faulty functioning duringoperation, the refining surfaces may contact each other. If this occurs,breakdown may result, or in any event, the refining surfaces will besubjected to considerable wear, which can significantly reduce theoperating time for these refiners. It is, therefore, very important toaccurately control the gap between the refining discs.

In order to accurately measure the distance between the refiningsurfaces, measuring systems have been employed which require preliminaryadjustment of the zero point; for example, immediately after therefining elements have been exchanged or replaced. In order to sodetermine the zero point of the measuring system, it is important thatthe contact position be determined. It has been known that the contactposition can be detected by utilizing sound measuring apparatus. Thismethod requires that a transmitter be mounted on one of the two refiningsurfaces. When the refining surfaces then contact each other, vibrationsare propagated through the refining disc to the transmitter, which canconstitute a microphone, impact pulsometer or vibrometer.

One disadvantage of this method is that the transmitter also measuresother sources of interference, such as the axle bearings. It istherefore difficult to detect a slight contact, and it is necessary forthe signal to "drown" out other sources of interference. This techniqueis also incapable of measuring or determining the phase position of thecontact point, i.e., the point or location where the refining surfacesfirst come in contact with each other. Another disadvantage of thesetechniques is that they presume that one of the two refining surfaces isstationary. Therefore, there are no present day methods for detectingthe contact point in the case of a pair of rotating refining surfaces.

SUMMARY OF THE INVENTION

In accordance with the present invention these and other disadvantageshave now been overcome by applicants' discovery of a method fordetermining the contact position between a pair of relatively rotatingrefining surfaces which comprises detecting the heat radiating from theinitial contact between the pair of refining surfaces during theirrelative rotation so as to generate an output signal and utilizing thatoutput signal to determine the contact position. In accordance with apreferred embodiment of the method of the present invention, the methodincludes determining the amplitude and pulse width of the output signalso that the magnitude of the heat radiating from contacting can becalculated.

In accordance with another embodiment of the method of the presentinvention, the method includes determining the rotation frequency of apair of relatively rotating refining surfaces, utilizing the outputsignal to determine the contact position comprising synchronizing theoutput signal to the rotation frequency for the purpose of determiningthe position of the contact point on the refining surfaces.

In accordance with another embodiment of the method of the presentinvention, the method includes determining the pulse width of the outputsignal and utilizing the output signal to determine the contact positionby utilizing the pulse width of the output signal to measure theparallelity of the pair of refining surfaces.

In accordance with a preferred embodiment of the method of the presentinvention, the method includes visually and audibly determining theoutput signal.

In accordance with another aspect of the present invention, apparatus isprovided for determining the contact position between a pair ofrelatively rotating refining surfaces comprises heat radiation detectingmeans for detecting the heat radiation generated by the contact betweenthe pair of relatively rotating refining surfaces from a positionradially displaced from the pair of refining surfaces.

In a preferred embodiment the pair of relatively rotating refiningsurfaces are enclosed in a refiner housing and the heat radiationdetecting means is mounted in the refiner housing. In a highly preferredembodiment, the heat radiation detecting means is located outside of therefiner housing and the apparatus includes coupling means for couplingthe heat radiation detecting means to the refiner housing fortransmitting the detected heat thereto.

In another embodiment of the apparatus of the present invention theapparatus includes amplifier means for visually and audibly presentingthe output signal.

In a general sense the present invention employs heat radiation from thecontact of refining surfaces for the purpose of determining the axialcontact position.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in considerable detail in thefollowing detailed description, in which reference is made to theaccompanying Figures, as follows:

FIG. 1 is a side, elevational, partially sectional, partially schematicrepresentation of one embodiment of the apparatus of the presentinvention;

FIG. 2 is a schematic representation of the method and apparatus of thepresent invention;

FIG. 3 is a schematic representation of a portion of the output signalfrom the transmitter signal used in accordance with the presentinvention;

FIG. 4 is a schematic representation of another portion of the outputsignal from the transmitter signal used in accordance with the presentinvention; and

FIG. 5 is a schematic representation of another portion of the outputsignal from the transmitter signal used in accordance with the presentinvention.

DETAILED DESCRIPTION

Referring first to FIG. 1, there is shown a disc refiner including tworefining discs, 1 and 2, which are arranged on two axles, 3 and 4, whichcan rotate in opposite directions. The axles are driven by motors, 5 and6, and one of the axles, 4, is also axially movable. The refining discsare provided with exchangeable refining elements, 7 and 8. The refiningsurfaces, 9 and 10, of the refining elements, 7 and 8, define a gap, 11.The refiner discs, 1 and 2, are enclosed by a refiner housing, 12. Chipsare supplied through an infeeder, 13, and through openings, 14, in oneof the refining discs, 1. A transmitter, 15, which is sensitive to heatradiation, such as a so-called photo-detector, is provided for thepurpose of detecting the frictional heat radiation which is generatedwhen the refining surfaces, 9 and 10, contact each other. Thetransmitter itself can be positioned in the refiner housing, 12, at alocation radially outside the gap, 11. The transmitter is directed tothe outermost edges of the refining surfaces, 9 and 10, because therefining elements, 7 and 8, are designed so that the distance betweenthe refining surfaces, 9 and 10, will be smallest at the periphery.

Since the temperature within the refiner housing, 12, can potentiallybecome quite high, it may in some cases be advantageous to position thetransmitter at a location spaced from the refiner housing. Thetransmitter can then be coupled to a special conducting device which isconnected to the refiner housing, 12, radially outside the refiningdiscs, 1 and 2. This conducting device can, for example, be a fiberoptic cable, which thus conducts the radiation from the place ofdetection to the transmitter.

When during their rotation the refining discs, 1 and 2, approach eachother, so that the refining surfaces, 9 and 10, eventually come intoactual contact with each other, the temperature increases, and heatenergy is generated at the point where that contact takes place. Thisrise in temperature is detected in the form of heat radiation by thetransmitter, 15. It is, thus, not the absolute temperature, but only therise in temperature which is detected. The transmitter then emits anelectric output signal, which can be utilized for the purpose ofdetermining the contact position. Due to the rotation of the refiningdiscs, the output signal of the transmitter will have the same frequencyas the rotation frequency. The amplitude and pulse width of the signalare proportional to the heat radiation. Since there are no other heatradiating objects, the sensitivity of the transmitter can be adjusted sothat a very slight contact can be detected thereby.

When the axles of the refiner are not correctly aligned, the parallelityof the refining surfaces, 9 and 10, is affected. Therefore, only aportion of the periphery of the refining surfaces initially comes intodirect contact. The phase position and extension of the contact pointare thus a measure of the parallelity between the refining surfaces.

By synchronizing the output signal to the rotation frequency of theaxle, and thus of the refining disc itself, the phase position of thecontact point of the refining surfaces can be determined. In addition,the pulse width of the output signal provides a basis for determinationof the extension of the contact point. It is therefore possible toutilize the output signal in order to measure the alignment of therefining discs, and thus of the axles.

The transmitter can also be coupled to an amplifier 16 in which theoutput signal is presented both visually and audibly for the purpose ofcalibrating the measuring system being utilized. Example

One of the axles in the disc refiner shown in FIG. 2 is provided with amechanical flag, 17, so that during rotation of the axle this providesimpulses to a second transmitter, 18. Thus, the second transmitter, 18,creates pulses which are synchronized with the number of revolutions,and which are repeated with a time period t₁. At a nominal rotation of1500 rpm, the time period is 40 ms.

The transmitter, 15, which is sensitive to heat radiation, is locatedperipherally offset in relation to the second transmitter, 18. In FIG. 2the locations of these two transmitters, 15 and 18, are shownschematically. The heat radiation from the contact point, 19, on therefining surface will be detected by the transmitter, 15, after the timet₂ when the contact point has rotated up to the transmitter, 15. Bystudying the displacement of the signal pulses from the twotransmitters, 15 and 18 (see FIG. 3), it is possible to determine thephase position of the contact point.

Depending on the peripheral extension of the contact between the refinersurfaces, the shape of the output signal varies. FIG. 4 shows an outputsignal which can be regarded in an oscilloscope. The amplitude of thepulse depends on how hard the contact is, and the width of the pulsedepends on the extension of the contact. FIG. 5 shows the signal from ahard contact from many different points. Thus, the output signals areindications of the parallelity between the refining discs, and thus ofthe alignment of the axles.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

We claim:
 1. A method for determining the contact position between apair of relatively rotating refining surfaces comprising detecting theheat radiating from the initial contact between said pair of refiningsurfaces during said relative rotation so as to generate an outputsignal and utilizing said output signal to determine said contactposition.
 2. The method of claim 1 including determining the amplitudeand pulse width of said output signal whereby the magnitude of said heatradiating from said contacting can be calculated.
 3. The method of claim1 including determining the rotation frequency of said pair ofrelatively rotating refining surfaces, said utilizing of said outputsignal to determine said contact position comprising synchronizing saidoutput signal to said rotation frequency for the purpose of determiningsaid contact position on said refining surfaces.
 4. The method of claim1 including determining the pulse width of said signal, said utilizingof said output signal to determine said contact position comprisingutilizing said pulse width of said output signal for measuring theparallelity of said pair of refining surfaces.
 5. The method of claim 1including visually and audibly determining said output signal. 6.Apparatus for determining the contact position between a pair ofrelatively rotating refining surfaces enclosed in a refiner housingcomprising heat radiation detecting means for detecting the heatradiation generated by contact between said pair of relatively rotatingrefining surfaces from a position radially displaced from said pair ofrefining surfaces, said heat radiation detecting means being mounted insaid refiner housing.
 7. The apparatus of claim 6, wherein a portion ofsaid heat radiation detecting means is located outside of said refinerhousing, and including coupling means for coupling said portion of saidheat radiation detecting means to said refiner housing for transmittingsaid detected heat thereto.
 8. The apparatus of claim 6 wherein saidheat radiation detecting means generates an output signal, saidapparatus including amplifier means for visually and audibly presentingsaid output signal.
 9. Contact position determining apparatus comprisinga pair of relatively rotating refining surfaces and heat radiationdetecting means mounted at a position radially displaced from said pairof refining surfaces for detecting heat radiation generated by contactbetween said pair of relatively rotating refining surfaces.
 10. Theapparatus of claim 9 wherein said heat radiation detecting meansgenerates an output signal and including amplifier means for visuallyand audibly presenting said output signal.